Added a ping interval on the client to ensure that auth tickets do not expire when there's lack of activity.

- This also involved adding a new configuration option 'pingInterval' which can be set via milliseconds in the connection.start

#2507
Added tests to verify that pingInterval behaves correctly with different configuration options in addition to multiple connection starts and stops.

- Also modified the existing tests which called ping interval by also passing in a transport (no longer need to do that).

#2507